1. Field of the Invention
The present invention relates generally to magnetic tape read and/or write heads, and more particularly to magnetic tape read and/or write heads with a slot formed on a supporting surface of the head.
2. Description of the Related Art
Magnetic tape continues to be an efficient and effective medium for data storage in computer systems. Increased data storage capacity and retrieval performance is desired of all commercially viable mass storage devices and media. In the case of linear tape recording, a popular trend is toward multi head, multi-channel fixed head structures with narrowed recording gaps and data track widths so that many linear data tracks may be achieved on a tape medium of a predetermined width, such as one-half inch width tape. To increase the storage density and reduce access time of magnetic tapes, data tracks on the tape are arranged with greater density and the tape is streamed by a tape head at increasingly faster rates.
Magnetic tape heads typically include an active device region including raised strips or ridges, commonly referred to as islands, that provide a raised tape support or wear surface with embedded transducers across which the magnetic tape advances. These embedded transducers can be either a recording element for writing information onto a magnetic tape or a reproducing element for reading information off a magnetic tape. An embedded recording element produces a magnetic field in the vicinity of a small gap in the core of the element, which causes information to be stored on magnetic tape as it moves across the support surface. In contrast, a reproducing element detects a magnetic field from the surface of magnetic tape as the tape moves over the support surface.
Generally there is a microscopic separation between an active device region of the tape head, including recording and reproducing elements, and the tape during operation that reduces the strength of the magnetic field coupled to the tape surface during the recording process. During the recording or reproducing process, the small separation reduces the coupling between the tape field and the reproducing element, causing a signal loss. This reduction in magnetic field strength is generally referred to as a “spacing loss.” The magnetic field strength detected by a tape or a reproducing element is proportional to e−kd/λ, where d is the head-to-tape separation, λ is the recording wavelength, and k is a constant. The detected magnetic field strength decreases exponentially both with respect to separation between the tape and the support surface and with respect to recording density (which is inversely related to the recording wavelength). Thus, while a limited amount of head-to-tape separation might be acceptable at low recording densities (100-200 KFCI), smaller transducers used with magnetic tapes of higher recording densities (over 200 KFCI) can tolerate little to no head-to-tape separation.
Further, to allow for faster access and write times, the media may be advanced by a head at speeds ranging from 100 to 1,000 inches per second or more. Increased media speed, however, may entrap air between a support surface of the tape head and the tape. The air may cause increased separation between the magnetic tape and the support surface leading to signal loss and/or excessive tape damage.
The amount of head-to-tape separation may be reduced by ensuring a proper wrap angle of the tape around the head structure to create tension in the tape and reduce the amount of air that may become entrapped. Typical wrap angles may range between about 0.1 and 5 degrees between the advancing tape and the supporting surface of the head structure depending on the particular application. If the wrap angle is too large, a bubble or arc may occur, creating a separation between the tape and the head structure. Further, if the wrap angle is too small the tape may entrap air as it advances over the head structure and increases the separation therebetween. Accordingly, high-speed tape drive systems are generally designed with precise tape paths and contoured tape heads to achieve a desired wrap angle. Manufacturing contoured tape heads with desired wrap angles is generally costly and complicated.
Additionally, increased tension and pressure to prevent spacing has several deleterious consequences. For example, increased tension and pressure may reduce tape life and increase the possibility of tape damage and data loss. Tape damage may lead to increased lateral tape motion and decreased reliability. Also, increased tension and pressure may cause the head structure to wear down more quickly resulting in shortened head life.
What is needed is a read/write head structure that presents an appropriate wrap angle to the magnetic tape to decrease spacing loss between the head structure and the magnetic tape. Further, a head structure with reduced manufacturing complexity and cost is needed.